Effect of clay content on the shear strength of clay\u2013sand mixture

Donghwi Kim,Heejung Youn,Boo Hyun Nam

doi:10.1186/s40703-018-0087-x

Donghwi Kim, Heejung Youn + Show 1 more

Open Access

https://doi.org/10.1186/s40703-018-0087-x

Copy DOI

Abstract

This paper investigates the effect of clay content on the shear strength of clay–sand mixtures. Bentonite and Jumunjin sand were mixed to prepare clay–sand mixtures with varying clay contents of 5, 10, 15, 20, 25 and 30%. The shear strength of clay–sand mixture was measured using direct shear tests and angle of repose tests in dry condition. The angle of repose of the clay–sand mixture was measured to be greater than that of pure sand for the studied range of clay contents. Likewise, the internal friction angle of the clay–sand mixture was measured to be higher than that of pure sand, reaching a peak at the clay content of 10%. Theoretically, the behavior of the clay–sand mixtures was to be governed by large size particles at clay contents smaller than 23.5%, which agrees well with the visual inspection on the mixtures. At clay content of 25.1% or greater, where the contribution of large particle was theoretically assumed to be none, the results from the angle of repose tests were significantly scattered, indicating that the clay started playing a key role in the behavior of mixtures.

Highlights

While soil mechanics have been developed based on the test results of pure sand or pure clay, the soils encountered in the field are mostly mixtures of various soils
The shear strength measured from both tests increased with the increase in the clay content at clay contents of low range, which was likely because the void of “loose state” sand was filled with clays
The internal friction angle of pure sand was 35.7°, which increased to peak value 38.7° at clay content of 10% and returned to 35.3° for 25%

Summary

Introduction

While soil mechanics have been developed based on the test results of pure sand or pure clay, the soils encountered in the field are mostly mixtures of various soils. The shear strength of clay– sand mixture with low fine content depended on the properties of large size particle, and the void of such mixture appeared to be partially filled with fines. The shear strength with different clay contents was measured, and results obtained from the tests were compared with respect to dry unit weight.

Results

Conclusion